1.1 该分类提供了基于测试方法中所述的三分之一倍频程频带冲击噪声级计算低频冲击噪声传输的单数额定值的方法 E492 和 E1007年 . 1.2 该分类定义了其他标准中未定义的评级。其他标准可能会根据该分类方法定义额外评级。 1.3 单位- 以国际单位制表示的数值应视为标准值。本标准不包括其他计量单位。 1.4 本标准并非旨在解决与其使用相关的所有安全问题（如有）。本标准的用户有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 1.5 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 4.1 LIR额定值的目的是描述低频冲击噪声，通常被称为“砰砰声”，主要由轻量化结构上的脚步声产生。随着地板-天花板结构的冲击声衰减增加，额定值增加。该评分与主观反应相关 3. , 4. 并可用于评估和比较低- 组件的频率影响噪声性能。 4.2 LIIC评级可用于相对比较，并对给定测试实验室内组件的低频性能进行排序。 5. 尚未测量实验室间LIIC的再现性，也未假设或建立实验室和现场额定值（LIIC和LIR）之间的关系。 注1: 当使用分类标准的度量时，应考虑低频测量不确定度增加的趋势。 注2: 此分类不能取代分类 E989 （冲击绝缘等级），不可互换。例如，组件的LIIC额定值并不决定其IIC额定值，不能用于表明符合IIC要求。 预期低频评级将与现有评级一起报告。 4.3 该分类只能用于三分之一倍频程数据。

1.1 This classification provides methods for calculating single-number ratings of low-frequency impact noise transmission, based on one-third-octave-band impact noise levels as described in Test Methods E492 and E1007 . 1.2 This classification defines ratings that are not defined in other standards. Other standards may define additional ratings based on the methods of this classification. 1.3 Units— The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 4.1 The purpose of the LIR rating is to describe the low-frequency impact noise, often referred to as “thudding,” primarily generated by footfall on lightweight structures. The rating increases as the impact sound attenuation of the floor-ceiling structure increases. This rating has been shown to correlate with subjective reaction 3 , 4 and can be used to evaluate and compare the low-frequency impact noise performance of assemblies. 4.2 The LIIC rating can be used for relative comparison and to rank-order the low-frequency performance of assemblies within a given test laboratory. 5 The reproducibility of LIIC between laboratories has not been measured, and the relationship between laboratory and field ratings (LIIC and LIR) is not assumed or established. Note 1: The tendency for measurement uncertainty to increase at low frequencies should be considered when utilizing metrics of classification standard. Note 2: This classification does not replace Classification E989 (Impact Insulation Class) and is not interchangeable with it. For example, the LIIC rating of an assembly does not determine its IIC rating and cannot be used to show compliance with an IIC requirement. The expectation is that the low-frequency ratings would be reported alongside the existing ratings. 4.3 This classification shall only be used with one-third-octave-band data.